Electric heater



1927. Jan 11 c. c. ABBOTT ELEGTRIC'HEATER Filed April 8. 1925 F1 5 //a t3 la 54 2a 2 Invenfor: Charles QAbbol'E H isArlor'neu.

'rseaauaau, 1927.

UNITED STATES m 0. ABBOTT, OI iussacnum'ra, ABSIGI'Q B T I'D-1C comm, AOOBPOBQAIOI O! m roan.

' merino a nuities fled a n s,-

M inventionv relates to electric heaters and as for its object theprovision of means for dissipating heat therefrom and for preventingoverheating of a certain part. or parts of the heater.

My invention relates more particularl to electric space heaters or airheaters suc as may be used in heating rooms, street cars, etc. One formof this type of heater is described and claimed in my-Patent No. 1,494,-939, dated May 20, 1924, of which this invention is an improvement. Incertain cases it is desirable to maintain the terminal ends of electricheaters at a comparatively low temperature, 'for example, where theterminalends are sealed with a material having a comparatively lowmelting int.

In"earrying out my invention I provide heating means for a centralsection of the heater, and heat dissipating vanes extending lengthwiseof the heater provided with slots near their ends whereby conduction ofheat to the ends of the heater is prevented. For a more completeunderstanding of my, invention reference should be had to theaccompanying drawing in which Figure 1 is 1. side view partially insection of an electric heater embodying my invention; Fig. 2 is asectional view alongthe line 2-2 of Fig. 1 looking in the direction ofthe arrows, while Figs. 3 and 4 are views similar to Figs. 1 and 2showing a modified form of my invention.

Referring to Figs. 1 and 20f the drawing, I have shown my invention inone form as comprising a helical coil, sheathed wire heating unit ofconvenient length, such as described and claimed in my Patent No. 1,367,341, dated February 1, 1921. Briefly, this heating unit comprises anouter metallic sheath 11 in which a helical resistance conductor 12 isembedded in acompacted mass of powdered-heat refractory insulating mterial 13. The insulating material 13 mag .be compacted to a hard densemass. having good heat conductivity by reducing the di; ameter ofthesheath after the unit has been assembled. Suchheating units can be benteasily into any desired shape and asshowh the unit 10 is bent in form ofa hairpin.

1 The resistance" conductor 12 extends throughout a central or bodysection 11' only of the sheath, and-has its ends connected toterminalmembers 14 and 15 which are also PATENT OFFICE.

I in

w. mussels-r...

The terminal mem extend thro the end portions 11" and 11 of the andproject from the sheathjor connection with a suitable source of electricsupply.

' For convenience in securing the terminals to theresistance conductor,the" ends of the terminals may be suitably threaded as indi} I cated byreference characters 16 and 17 and the turns of the resistance.conductor screwed on'these threaded portions. This forms a goodmechanical as well as electrical connec ion. Y As shown, each end of thesheath is sealed to prevent the entrance of moisture. For exam le, eachend of the sheath 11 may be thre ed at 18 for a short.'distance,"and acup-like member or receptacle 19. having a threaded bore screwed on thethreaded end 18. The member 19 is filled with a suitable sealin material20 such as bakelite or an aspha tic compound. This sealing material ispoured into the member 19, the unit being d-upright with the member 19uppermost,

while heated to thinly liquefy 1t; The threaded end of the sheathextends into the interior of the cupv a slight distance only. Suitablyconnected to the ends of the terminal members 14 and-15, as by brazing,are copper connectors. 14 and 15'. These connectors extend into the cupmembers in close proximity to the ends of the sheath, a short gap beingleft between the inner end of each connector and the end of the sheath,which gap is filled with the sealing material 20. The inner ends of theconnectors are beveled to allow the sealing material to flow readilyinto these sealing material fill e gaps thoro y and make a good firmconnection with e insulating material 13, which is exposed at the endsof the unit, so that there will be no air gaps and otheroveak points inthe formed by the sealin material between the terminal members and theends of the sheath. The sealing material surrounds the connectorsto thelevel ,of the cup members which have their inner edgesbleveledllzloprovide ter cree age space tween t e connect dr and this sheath.provided with vrtions 14" and 15 gaps. It is essential that the- Theconnectors arewhich' are embedded in esealing material embedded the 118.For the purpose f-dissipating the heat nerated by the unit 10, the unitis clamped tween two metallic plates 21 and 22 extending lon itudinallythereof and forming together a eat dissipating member. The plates areformed with registering hairpinshaped grooves or recesses 23 and 24respective y in which the heatin unit 10 is placed and secured bywelding the plates together as near the heatingumt as ossible in suchmanner as to clamp the heating unit tightly and form a and thermalcontact with the sheath 11. e welding of-the plates ma be carried out inany suitable manner, sue as by a line welding or spot welding process.

The clamping plates 21 and 22 extend throughout the entire length of thehairpinshaped unit 10, covering the central portion 11 and the two endportions 11 and 11. In order to interrupt the conduction of heat fromthe central portion 11 to the ends of the unit, slots are formed in theplates. As shown in Fig. l'an internal slot 25 is formed in the platessubstantially at the junction of the resistance conductor and theterminal members. This slot -25 terminates at each end a short distancefrom the edge of the plates and serves to interrupt the continuity ofthe plates in a region adjacent the heating unit. .Two additionalinternal 'slots 26 and 27, similar to slot 25, are provided at suitableintervals between the slot25 and the ends of the heating unit. Betweenslots 25 and 26 are two aligned external slots 28 and 29 which are cutin toward each other from opposite edges of the plates.

These slots extend toward each other far enough to break away the metalof the plates around the heatingunit. Slots 30 and 31, imilar to slots28 and 29, are provided between slots 26 and 27 Bymeans of the slots'25t0 31 inclusive, it will be observed that the metal of the, plates isbroken away adjacent the heatingfiinit- 1n such manner as to interruptthe condu tion of heat through the lates, but witnput materiallyimpairing t e'heat dissipatmg'characteristics of the plates. It willalso I be observed that any heat which is conducted 14 and 15. It is forthis reason that the inner ends-of the connectors fare brought own nearthe bottomsof the cup toward theend of the heating unit must follow azigzag course through the plates. This construction-plays an importantpart in maintaining the ends of the heating unit at a comparatively lowtemperature at which the sealing material 20 is not melted .orappreciablysoftened. The ends of the heating unit are also cooledby'conduction through the connectors down as near as possible to theendsof the sheath. Furthermore-by terminating the 'ends of the sheath nearthe bottoms of the 1p members, the connectors are brought members sothat lower temperatures are mamtained at of the heating unit.

heat will be conducted through the sheath 90 these points, and thereforeany tendency for the sealing material to be melted at the bottoms of thecup members is ove come.

In order to provide for more effective dissipation of heat by the plates21 and 22,

the plates are cut or slit from the slot 25 in a direction parallel withthe two branches of the heating unit-to a point near the bend of theheating unit. As indi ated in Fig. i

2, this cut in the plate 21. is near the lower branch of the heatingunit, while the cut in the plate 22 is near the uppenbranch 'of theheating unit. The two overlapping vanes 32 and 33 thus formed are bentapart to provide for the circulation of air between adjacent the centralportion 11 of the heat- 86 ing unit substantially independently of thedissipation of heat by the ortions of the plates adjacent the endortions 11" and 11 small amount of 11', the terminal members 14 and 15and other parts toward the ends of the heater,

but this heat will be rapidly dissipated.

In .the modified form of my invention shown in Figs. 3 and 4.- theheating unit 35,

which is similar in construction to the heating unit 10, is shown as astraight length clamped between two metallic strips 36 and 37-. Sincethe ends of the heater are identical in construction, only one end willbe described in detail. Slots 38 and 39 are cut in the plates fromopposite edges toward the heating unit at the junction betweentheresistanceronductor and the terminal. mernber 40. Similar slots 41 and12 are pro- 106 however, a difierent form of connector,

shown. as a binding post 47, is secured, as by brazing, to the end ofthe terminal member 40 in place of the connector of Fi 1. This bindingpost. serves to conduct heat away-from the-eiiil oftheheating unit inthe manner previously described in connec- }tion with Fig. 1. Thebinding post receives heat by conduction from the end of the heatingunit, which heat is dissipated intothe surrounding air, and has anappreciable effect in cooling the end of the heating unit.

While I have described my invention ge embodied in concrete form and asoperatingin a specific manner in accordance with the througha section ofsaid sheath, a terminal for said resistance conductor extending throughan end section of said sheath, and heat dissipating means extendinglengthwise of said sheath in heat conducting rela- "tion therewith,thecontinuity of said heat is dissipated from said sections independ-'dissipating means being interrupted substantially at the junction ofsaid resistance conductor and said terminal, whereby heat ently oeachother.

2. An electric heater comprising a metal lic sheath, a resistanceconductor extending through a section of said sheath, a terminal forsaid resistance conductor extending through an end section of saidsheath, and a heat dissipating member extending lengths wise of saidsheath provided with a slot at the junction of said resistanceconductor. and said terminal for interrupting the conduction of heatthrough said member to the said end section.

3, An' electric heater comprising a metal- --lic sheath, a resistanceconductor in a body section of said sheath,- a' terminal for saidresistance conductor extending through an end section'of saidsheath,powdered heat refractory insulating material, surrounding saidresistance conductor and terminal, and a heat dissipating memberextending length wise in heat conducting relation with said sheath, saidmember being provided with a slot adjacent the 'unction of said sect onswhereby heat is dissipated from said tody section substantiallyindependently'of said end section.

4. 'An electric heater comprising a metallic sheath, a resistanceconductor located in a central section of said sheath, terminals forsaid resistance conductor extending through the end sections of saidsheath, powdered heat refracto insulating material compacted aroun saidresistance conductor and terminals, and a pair of metallic platesforming heat dissipating means between which said sheath clamped, saidplates being provided with slots at the junctions of said centralsection with said end sections whereby heat is dissipatedfrom said endsections independently of said central section.

5. An electric heater comprising a U- shaped heating unit, a pair ofmetallic plates forming heat dissipating means be-- tween which saidunit is clamped, said plates being slit and shaped to allow circulationof air between the branches of said U-shaped unit and provided with aseries of internal-and external slots for interrupting the conduction ofheat to the ends of said unit.

6. An electric heater comprising a metal- 1 lie sheath, a resistanceconductor secured in said sheath in electrically insulating relationtherewith, a receptacle securedto the end of said sheath, a sealingmaterial in said receptacle, and a'relatively heavy heat conductingmember electrically connected to said resistance conductor extendinginto said sealing material in close proximity to said sheath.

7. An electric heater comprising a metallic sheath, a resistanceconductor secured in said sheath, a terminal member for said resistanceconductor projecting from said sheath, powdered heat refractory materialin said sheath surrounding said resistance conductor and terminal, arelatively heavy heat dissipating connector secured to said terminalnear the end of said sheath, a receptacle secured to the end of saidsheath,

and a sealing material in said rece tacle

